The present invention relates to a composition useful as prophylactic and therapeutic agent for the management of viral diseases in aquatic animals, said composition containing aqueous extract of selected plants. The present invention also relates to a process for preparing the composition and a method of treating white spot syndrome virus (WSSV) infected tiger shrimp Penaeus monodon. 
In the tropics, particularly in Asian subcontinent, shrimp aquaculture has been growing as a major enterprise due to its export market and high profitability. In India, shrimp farming has transformed from a traditional farming practice into an organized industry in a short period of time. More than 100,000 hectares of coastal land are being used for shrimp farming in India, producing  greater than 80,000 tones annually (C. T. Achuthankutty, 1998. Sustainable shrimp farming in Indiaxe2x80x94Prospects and challenges. In Technological Advancements in Fisheries, Edited by M. S. Hameed and B. M. Kurup, Publ. No.1, School Indl. Fish., Cochin University of Science and Technology, Cochin, p. 54-59). Different species of shrimps are being cultivated in different parts of the world, but the tiger shrimp, Penaeus monodon is the most favored species for farming in India.
Since 1992, the shrimp culture industry, particularly in Asia, has been threatened by a viral syndrome, commonly known as the xe2x80x98white spot diseasexe2x80x99, causing heavy mortality and financial losses (Y. G. Wang; M. Shariff; P. M. Sudha, P. S. S. Rao; M. D. Hassan and L. T. Lan, 1998. Managing white spot disease in shrimp, Infofish International, 3:30-36). Several species of penaeid shrimps viz. Penaeus monodon, P. japonicus, P. chinensis, P. indicus, P. merguiensis and P. setiferus have been known to be infected by this virus and the losses reported in China during 1993 was about U.S. $ 1 billion and in Thailand during 1996 was U.S. $ 500 million (Fishing chimes (as reported in Global Aquaculture Advocate Vol 2, Issue 2), 1999. What is shrimp white spot disease?, 19: 21-22). The outbreak of the disease was first noticed in India in the Kandaleru creek fed brackishwater farms along the Andhra coast during 1994 (K. M. Shankar and C. V. Mohan, 1994. Kandaleru-fed brackishwater farms near Gudur, A. P., Fishing Chimes, September 23-24). Since then it has spread to shrimp farms located along both the coasts and caused heavy mortality and revenue loss to the farmers (C. V. Mohan, 1996. Health management strategy for a rapidly developing shrimp industry: An Indian perspective, In Health Management in Asian Aquaculture. Proceeding of the Regional Expert Consultation on Aquaculture Health Management in Asia and the Pacific, Edited by R. P. Subasinghe, J. R. Arthur and M. Shariff, Fish Tech Pap No. 360, FAO, Rome, p. 75-87). The estimated revenue loss in India for the year 1995-96 was about Rs. 250-300 billion (I. Karunasagar and I. Karunasagr, 1999. Shrimp disease prevention methods with special reference to white spot disease. Paper presented in the Workshop on Development of Sustainable Management Practices in Shrimp Farming under World Bank Assisted Shrimp and Fish Culture Project, held at Bhubaneswar, Jul. 30-31, 1999). The causative viral agent has been known by different names in different countries such as haematopoietic necrosis baculovirus (HHNBV), systemic ectodermal and mesodermal baculovirus (SEMBV), penaeid rod-shaped DNA virus (PRDV), white spot baculovirus (WSBV), Penaeus monodon non-occluded baculovirusII (PmNOBII), Penaeus monodon non-occluded baculovirusIII (PmNOBIII) (C. V. Mohan; P. M. Sudha; K. M. Shankar and A. Hedge, 1997. Vertical transmission of white spot baculovirus in shrimps-A possibility? Curr. Sci., 73: 109-110; I. Karunasagar; S. K. Otta and I. Karunasagar, 1997. Histopathological and bacteriological study of white spot syndrome of Penaeus monodon along the west coast of India, Aquaculture, 153: 9-13; Y. G. Wang; M. Shariff; P. M. Sudha, P. S. S. Rao; M. D. Hassan and L. T. Lan, 1998. Managing white spot disease in shrimp, Infofish International, 3:30-36). However, the etiology of the viral agent known by different names has been well studied and has been confirmed to be a baculovirus and is collectively known as the white spot syndrome virus or WSSV (D. V. Lightner, 1996. Handbook of for diagnosis procedures for diseases of penaeid shrimp, Special Publication of the World Aquaculture Society, Baton Rouge, La., Section 3.11). WSSV has been shown to target various tissues originating from both the mesoderm and ectoderm as evidenced by histopathological studies (C. Wongteerasupaya; J. E. Vickers; S. Sriurairatana; G. L. Nash; A. Akarajamom; V. Boonsaeng; S. Panyim; A. Tassnakajon; B. Withyachumnamkul and T. W. Flegel, 1995. A. non-occluded, systemic baculovirus that occurs in cells of ectodermal and mesodermal origin and causes high mortality in the black tiger prawn Penaeus monodon, Dis. Aquat. Org., 21: 69-77) and in situ hybridization ((P. S. Chang; C. F. Lo; Y. C. Wang and G. H. Kou, 1996. Identification of white spot syndrome associated baculovirus (WSBV) target organs in the shrimp Penaeus monodon by in situ hybridization, Dis. Aquat. Org., 27: 131-139). These studies were conducted on farm produced shrimps and/or experimentally infected shrimps. In another study, the virus has also been detected in different organs/tissues including the reproductive organs of wild caught brooders of Penaeus monodon indicating its vertical transmission (Chu-Fang Lo; Ching-Hui Ho; Chau-Huei Chen; Kuan-Fu Liu; Ya-Lin Chiu; Pie-Yan Yeh; Shao-En Peng; Hui-Chen Hsu; Hwei-Chung Liu; Chen-Fang Chang; Mao-Sen Su; Chung-Hsiung Wang and Guang-Hsiung Kou, 1997. Detection and tissue tropism of white spot syndrome baculovirus (WSBV) in captured brooders of Penaeus monodon with a special emphasis on reproductive organs, Dis. Aquat. Org., 30: 53-72).
Some plants have been used to control the severity of certain types of viral diseases. The ethanol extracts of two species of the genus Phyllanthus vis. P. amarus and P. urinaria homogenised with lobster haemolymph medium and injected into healthy Penaeus monodon after mixing with the yellow-head baculovirus (YBV), showed antivirucidal activity at a concentration of 100 xcexcg/ml and 1 mg/ml, respectively against yellowhead baculovirus (YBV) (S. Direkbusarakom; A. Hurunsalee; S. Boonyaratpalin; Y. Danayadol and U. Aekpanithanpong, 1993. Effect of Phyllanthus spp. Against yellow-head baclovirus infection in black tiger shrimp, Penaeus monodon, In Diseases in Asian Aquaculture II, Fish Health Section, Edited by M. Shariff, J. R. Arthur and R. P. Subasinghe , Asian Fish. Soc., Manila, p. 81-88). However, these extracts have not been tested on the WSSV.
The ethanol extract of the leaves of Thai traditional medicine against human viral disease viz. Clinacanthus nutans Lindua, injected into the tiger shrimp showed inhibition of the yellow-head rhabdovirus (YRV) at a concentration of 1 xcexcg/ml and by oral application at the rate of 1 g/kg of pellet feed (S. Direkbusarakom; L. Ruangpan; Y. Ezura and M. Yoshimizu, 1998. Fish. Pathol., 33: 401-404). This extract has also not been tested on controlling the WSSV.
The Gauva leaf (Psidium guajava), was not found to be effective on yellow-head virus infection in tiger shrimp although it was effective in preventing bacterial infection in cat fish (S. Direkbusarakom; A. Herunsalee; M. Yoshimizu; Y. Ezura and T. Kimura, 1997. Efficacy of Guava (Psidium guajava) extract against some fish and shrimp pathogenic agents, In Diseases in Asian Aquaculture III. Fish Health Section, Edited by T. W. Flegel and I. H. MacRae, Asian Fisheries Society, Manila, p. 359-363).
It has been reported that the extract of an Indian wild plant, xe2x80x98Swallow Wortxe2x80x99 is useful in combating white spot virus (Anonymous, 1997. Wild plant combats WSV, Infofish International, No.2, March/April, 1997). However, no details on the therapeutic dosage and effects have been made available.
There also appeared a report that the extract of the weed Calotropis gigantea is able to arrest mortality in white spot infects shrimps (MPEDA, 1996. Herbal treatment for shrimp virus, UNI report in Indian Express, Jul. 18, 1996), but did not mention the dosage and related details.
The main objective of the present invention is to provide a composition useful as prophylactic and therapeutic agent for the management of viral and bacterial diseases in aquatic animals.
Particularly, the objective of the present invention is to provide a composition useful for improving health and reducing mortality rate in tiger shrimp Penaeus monodon. 
More particularly, the objective of the present invention is to provide a composition for the treatment of white spot disease in the tiger shrimp Penaeus monodon. 
Another object of the present invention is to provide a process for the preparation of the composition useful as prophylactic and therapeutic agent for the management of viral and bacterial diseases in aquatic animals.
Yet another object of the present invention is to provide a method for reducing the mortality rate in the tiger shrimp Penaeus monodon. 
Still another object of the present invention is to provide a method for the treatment of white spot disease in the tiger shrimp Penaeus monodon. 
The present invention relates to a composition useful as prophylactic and therapeutic agent for the management of viral and bacterial diseases in aquatic animals. The invention also relates to a process for the preparation of the composition and a process for the treatment of the aquatic animals using the said composition.